Report agent host build info via RootState._meta

[roblourens]

What

Surfaces the hosting VS Code CLI's build info (version, commit, date, quality) to agent host clients so they can tell which build is hosting a given agent.

The info is carried on a well-known hostBuild key inside a new optional RootState._meta property bag. RootState is delivered as a snapshot at connect time, so every local and receives it reliably, with no protocol-level message addition required.remote client

Why _meta on RootState

• RootState is the agent host's own state and is sent as a snapshot inside the initialize response, reaching all clients deterministically.
• Connect-time logging was considered and rejected: the OTLP logs channel has no replay buffer and clients subscribe only after initialize, so a log emitted during connect never reaches remote clients.

Changes

• Add optional _meta?: Record<string, unknown> to the generated RootState (matches the merged protocol change).
• Add host build info helpers in sessionState.ts: IHostBuildInfo, readHostBuildInfo, withHostBuildInfo, formatHostBuildInfo, hostBuildInfoFromProduct.
• AgentHostStateManager seeds _rootState._meta from a new hostBuildInfo option, wired from the product service in agentService.ts.
• RemoteAgentHostLogForwarder writes a one-time Agent host version ... header into the Output channel on attach.

Note: only the additive _meta field is taken from the protocol here. The broader protocol sync (changeset/session restructure that has accumulated on protocol main) is intentionally left out of this it's an unrelated breaking change that needs its own consumer updates.PR

(Written by Copilot)

[Copilot]

Pull request overview

This PR exposes the hosting VS Code CLI’s build metadata (version/commit/date/quality) to Agent Host Protocol clients by adding an optional RootState._meta property bag and standardizing a well-known hostBuild entry. This makes it possible for remote clients (and log output viewers) to identify exactly which host build they are connected to without adding new protocol messages.

Changes:

• Adds _meta?: Record<string, unknown> to the protocol RootState and introduces hostBuild helpers (IHostBuildInfo, read/write/format/fromProduct) in sessionState.ts.
• Wires host build info into AgentHostStateManager via a new hostBuildInfo option, seeded from IProductService in AgentService.
• Adds coverage for helper behavior and root-state seeding, and prints a one-time “Agent host version …” header into the forwarded remote OTLP logs Output channel.

Show a summary per file

File	Description
src/vs/sessions/contrib/providers/remoteAgentHost/browser/remoteAgentHostLogForwarder.ts	Writes a one-time host build-info header into the remote agent host log Output channel.
src/vs/platform/agentHost/test/node/agentHostStateManager.test.ts	Adds tests ensuring _meta.hostBuild is seeded (or omitted) as expected.
src/vs/platform/agentHost/test/common/state/hostBuildInfoMeta.test.ts	Adds unit tests for the _meta.hostBuild helpers (round-trip, validation, formatting).
src/vs/platform/agentHost/node/agentService.ts	Passes host build info (derived from IProductService) into the state manager options.
src/vs/platform/agentHost/node/agentHostStateManager.ts	Adds a hostBuildInfo option and seeds RootState._meta using withHostBuildInfo.
src/vs/platform/agentHost/common/state/sessionState.ts	Introduces RootMeta/hostBuild conventions and helper utilities for reading/writing/formatting host build info.
src/vs/platform/agentHost/common/state/protocol/channels-root/state.ts	Extends the protocol RootState type to include the optional _meta property bag.

Copilot's findings

• Files reviewed: 7/7 changed files
• Comments generated: 2